1. Field of the Invention
The invention relates to improved dog driving arrangements in self-reversing tapping attachments, which are tools carrying taps for threading and are connectable to an external drive source such as a driving machine, the tapping attachment including means for reversing rotation of the tap.
2. Description of the Prior Art
Related patents to the same inventor as named on the application herein are U.S. Pat. Nos. 3,397,588; 3,472,347; 3,717,892; 3,946,844; 3,999,642; 4,014,421; 4,029,429; 4,067,424; and 5,011,344. The above-cited patents relate to provisions in tapping attachments for direct drive and for reverse drive as well as driving arrangements therein, among other things.
Tapping attachments have been extensively utilized in technology and industry for a lengthy period of time, and the field constitutes a well-developed art. With the advent, however, of Computer Numeric Control (CNC) of tapping operations and other instances of high-speed, high performance tapping, a need for improvement has become noticeable in particular with respect to self-reversing tapping attachments. Self-reversing tapping attachments are those which afford the capability of reverse rotation of a tap after it has reached the selected depth, for the purpose of facilitating its withdrawal from the hole which has been threaded by it.
One of the most common means for imparting rotation in existing tapping attachments is the dog drive. In a dog drive, drive is transmitted through a driver element to a drive spindle holding the tap, the driver element having drive dogs for engaging with the spindle and being driven by dogs or splines on forward and reverse driving members.
In existing dog drives impacts between the components and parts involved with driving, such as dogs and splines, cause shock and vibration resulting in wear of the machine elements. This is particularly pronounced in high speed applications such as those relating to CNC operations. In addition, in existing arrangements, particularly those relating to high speeds of rotation, there is a need for rapid change between forward and reverse modes of rotation. In existing tapping attachments, there are limitations with respect to such changing between rotational modes due to the configurations of the driving elements which due to their shape and size may interfere with one another during attempted shifting and clutching.
Therefore, there has been a felt but unfulfilled need for a dog drive in a tapping attachment whereby shock and wear within the driving and clutching elements are minimized, and providing facilitated shifting between forward and reverse modes of rotation.